Kage
Mudduck
Posts: 11
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Post by Kage on Sept 28, 2019 1:53:00 GMT -5
I had that exact CB at one point but can't place when I found it in the trash or garage sale, no offence, but I am a thrifty younger person who grew up in the 90s with CBs before the web and internet really took off for us in school. It was a nice little 23er as I recall. Oh yeah and that old Radio Shack power supply. It says 3 amps but can honestly push up to 4 before the regulator gets angry. I later parted out the power supply when converting a car stereo amplifier to house use in desperation as a kid before I got some decent stereo systems. The regulator in that thing is a tough cookie and was built with a good quality transformer.
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Kage
Mudduck
Posts: 11
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Post by Kage on Apr 20, 2019 2:28:09 GMT -5
I don't know whether you are still around or not but looking at your design, made me want to ask (about that frequency counter module). I have the 8 digit one and, cheapskate that I am, had visions of using it more or less as a bench counter. The one thing that I am uncertain of is the sensitivity. I think it says that in the low range it is around 60mv p-p. In your opinion do you think that this would work well enough to use probing around inside a radio as it is? If not, would a high frequency preamp help to insure it?? Thanks in advance if you should see this! Bob Yeah I am still around. Been a while since visiting. If I were to use one as a bench counter I would certainly add a few things. For one at bare minimum diode limiter input protection, like 1N4148 diodes back to back in parallel to limit AC input to <0.7v and a few hundred ohm resistor before them for current regulation to act as a protection circuit. I forget what the sensitivity is of these counters but it sure couldn't hurt to add a JFET front end to it if you want it to sense weak signals or even off a sniffer antenna. It certainly would be fairly simple to add, and the diodes ahead of it would protect the JFET gate from static and large voltage swings. Eventually I might do something similar and get back to posting a circuit idea. Sorry for the long away time, life and things..
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Kage
Mudduck
Posts: 11
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Post by Kage on Oct 28, 2017 10:13:14 GMT -5
have you had any problems with the frq count on the vfo I heard the the voltage regulator is to small and burns out I also heard about that being an issue. Even though originally I was running the full 13.8v to the counter I decided it would be smart to play safe so I added a 7808 voltage regulator to it. For people who don't have an 8 volt regulator I'd be willing to bet gluing on a chunk of metal to the onboard regulator would help keep it cool. The counter needs to stay cool anyways being as it's inside the same box as the VFO. Any fast and large temperature variations would mess up the VFOs stability, even with temperature compensating capacitors and a distance you'd be surprised how little it takes to throw things off if a regulator gets warm fast in the same unit. I honestly find it hard to believe that the onboard voltage regulator for the counter would burn out given I have never felt it get warm. Makes me wonder if people are giving it more than the 15 volts the specs say is the maximum? I keep mine on lowest LED brightness though, I find the higher brightness levels to be an eye killer with that bright blue. Either way no issue luckily. I did have to play with the one potentiometer on the counter that sets where it triggers and seems to adjust its sensitivity. I think that was slightly off from the factory.
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Kage
Mudduck
Posts: 11
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Post by Kage on Oct 5, 2017 13:46:19 GMT -5
Thanks for the replies. Yeah like I said the cbtricks website is incorrect in its schematic. I'm not worried about getting more carrier out now. It was an issue when I got it and I had the idea in my head that the little bump in RF out meant something realistically but even then I knew it was a fruitless effort trying to get more out w/o stressing the RF output device. Reality is the modulator in this radio should be fully capable of some serious modulation given it's push pull with two modulator transistors and recently I replaced the original modulation transformer in it with one out of an old scrapped Johnson 123. Yes I know it's a sad swap as the Jonnson was worth more but it was already in my part bin from years ago. The new tranny allows a hell of a lot more modulation and RF output with a ton of headroom. Johnson really didn't joke around. Also after sweeping the audio in to the mic I noticed a large improvement in bandwidth in audio for TX. Neat little upgrade, not sure how many here have ever tried swapping modulation transformers but it can make a dramatic difference. This radio can now sweep a huge range of audio coming close to HIFI that some ops want w/o the need to go to series modulation. Eventually I will post some pics and circuits of my franken CB lol.
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 30, 2017 17:46:25 GMT -5
Most of the older 23 channel rigs had limited bandwidth, since they only needed to cover 300 Khz. Yeah made my first decent contact the other night to someone around 8 1/2 miles from my town running barefoot into an EFHW dipole mounted up 20'. Took me by surprise considering they were giving me around S6 off their mobile and said my signal is big and booming Then there's other people who I swear buy the smallest magmounts and I wonder why I can barely talk to them under a mile away until they tell me what they are using. I still prefer skip since it's fun to see how far I can cast that signal and don't have to worry about the occasional unsavory local types that pop in and out to stir up trouble. Anyways, still curious to find a schematic eventually for this radio but maybe that's a pipe dream at this point.
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 27, 2017 13:26:24 GMT -5
After tracing out the RF output section by eye onto paper I found that the buffer PA transistor had a air coil slug that could easily be adjusted to get the TX section out to 27.700 but that's about the limit before the TX begs for mercy. Removing the slug wasn't the answer as it introduced harmonics but right below the maximum the transmit stage could handle the TX out to there with respectable power. Any frequency beyond that point introduces spurs and harmonics with reduced power, so the limit of the Five by Five radio is from 26.515 to 27.700 TX. With the VFO it covers this well w/o harmonics that are problematic. Receive is a bit wider covering 26.300 to 28.100 w/o much of any change. It's possible to receive up to 28.900 as I've found but birds exist up there and the RF gain drops bad. Changing that slug also increased output power across the entire band while still maintaining full stock modulation besides on the skirts of the range which I wouldn't use for TX anyways. Looking at what I jotted down it seems it's simply a HPF stage on the output of the buffer amp transistor before the final RF stage so that makes sense. I'll post more info about the mod eventually, but it's sickingly golden screwdriver, but I really did check the scope and final output and for harmonic/spur issues. It only increases TX out to 4.0-4.2 watts and expands the TX high frequency range, that's it. The 50MHz trap coils are still doing their job and it's still clean output. Nice to know some 23ch radios can still do what 40ch radios can with a little mod like this. It's still transmitting with headroom so 100% modulation is no issue. I like this radio a lot, it's simple and easily modifiable. Going to buy a Albrecht 6110 or as it's called for US "Anytone Smart CB". I've been really wanting one of those because they seem capable out of the box for range and frequency capability. I really miss my SSB rigs I had in the past, but getting back into this hobby, and AT THE WRONG TIME given the low solar cycle, but even right now as I type this there is lots of Mexican skip so maybe there is a window of hope?
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 20, 2017 10:59:29 GMT -5
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 20, 2017 10:55:49 GMT -5
Hi all, I have this radio and it's similar to other Teaberry radios of that era but the schematic on cbtricks is not correct. The manual and service manual are right but the schematic they linked is for a different radio. The one I have is a 4 pin mic, uses a 2SC756 for the final RF amp. Curious if it's possible to get a bit more power out of this since it's a 70s radio and manufactured to put out 3.2 watts carrier. The RF power transistor should be able to provide a bit more w/o taking a golden screwdriver to the traps and other nonsense. Wondering if the B(base) of the transistor has a low value resistor to ground to limit RF output or something obvious that can be modified to get her up to a full 4 watts without downward swing to cancel out the loss of power in my 100' of old RG 8/u coax out to the tower. I suppose this is pulling hairs considering how little of a difference there is in RF power output between the 3.2 and 4 watts considering few would notice on their S-meter, but simply wondering, and I can't find the actual schematic online anywhere. Also would love to get the receive to pull out well beyond 27.255. With the VFO I can get it to cover well out to channel 40, but beyond that the receive sensitivity drops off fast when taking it to freeband frequencies. Wondering if adjusting the IF coil section could help with this but I'd need the schematic to see what I am doing. Thanks.
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 15, 2017 8:23:46 GMT -5
I am curious why you decided to go "old school" analog VFO and not try either a PLL circuit or a direct frequency generator, as these seem to be more stable than a VFO. I like your final construction. Looks almost commercial. It's also nice that we have frequency counters that can plug right in. Sure beats having to create an analog dial and linearizing it through its range. Good luck with the project. Hope to hear more about it. I went with the LC type VFO for simplicity, plus being as it's a Vackar type oscillator and tuned using the coil instead of a variable capacitor the stability is very good with a large frequency span without having to use a switch to change band ranges. The other reason is that modern direct digital synthesizers often have noise on their output which can cause issues reception noise, birdies, transmit spurs and so on. It takes a bit to clean up that signal to be useful whereas a simple transistor oscillator can be made to have an extremely clean output and low phase noise. PLL circuits are nice but once again add complexity. I know there are huff&puff stabilizers that can be added on so that's always a future option but may be overkill for this use. I guess the only thing I wanted digital in this project was the frequency counter for practicality, after all I am attaching this to older CB radios so it just feels right using something less modern to pair with them. Thanks for the input and warm welcome
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Kage
Mudduck
Posts: 11
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Post by Kage on Sept 14, 2017 5:41:26 GMT -5
Hello, new here to this forum. I run a similar message forum but it's more related to pirate radio on shortwave and broadcast AM/FM along with the technically geared types that like to do their own DIY projects. Been in CB radio since I was a kid and felt the itch to play around with the 11m band again. Got my hands on an older 23 channel Teaberry Five by Five and modified it heavily over the last few years. One thing I have been wanting to do is attach a VFO so I can cover the full 40 channels, and the freeband channels along with amateur 10m which the latter will be nice when licensed. Yeah lazy on that one because there are no VE's near me Yes I know the legality of using a VFO with CB radios, it's legal to use for reception so for now lets just say that's what I am using it for. I don't mean to cross-link to another proboards forum if that's against rules but I wrote up a long thread about the project on my own forum with plenty of pictures kind of like a blog so it would be redundant to post the same stuff here.. darkliferadio.proboards.com/thread/891/high-stability-radio-project-blogHere is what the final design looks like sitting next to the old Uniden Teaberry... I took a lot of time studying how the Siltronix VFO works along with the PAL. The PAL is obviously better because it mixes a lower VFO frequency with a crystal oscillator for stability. Getting my VFO to work with little drift was no easy task but the permeability tuned oscillator plus quality capacitors made it come to the stability of the PAL if not better. I get around +-2hz per minute drift, plenty good for AM and SSB. I may improve on this eventually but I doubt I can get it down to <8-10Hz per minute in high temperature changes outside of ambient house temp. That's okay though because I plan to use it indoors only. Been hearing people talk on 27.505AM lately if I recall correctly. I have the parts now to stick up a EFHW antenna I am making out of 17' conduit pipe and a piece of PVC for a tower insulator. Hope this little project pays off and is able to make the range to them with my barefoot radio, VFO, and half wave vertical once constructed. Hope I am welcome here. I love older radios, may be 32 y/o but always been a tube guy and DIY type that loves designing and repairing electronics, so.. Hi!
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